Pump device

ABSTRACT

A pump device includes a flow control valve that returns a part of working fluid discharged from a pump to the suction side, and the flow control valve includes a valve body, a first fluid pressure chamber that is provided so as to face against a first-side end surface of the valve body and that is communicated with a discharge channel, a second fluid pressure chamber that is provided so as to face against a second-side end surface of the valve body and that is communicated with the discharge channel, a biasing member that is accommodated in the second fluid pressure chamber for biasing the valve body in the valve-closing direction, and a pressure regulator that is provided in a communicating passage through which the discharge channel is communicated with the second fluid pressure chamber and that adjusts pressure in the second fluid pressure chamber.

TECHNICAL FIELD

The present invention relates to a pump device.

BACKGROUND ART

In the related art, there are known pump devices, in which a flow control valve is provided in order to keep a discharge flow amount of the pump constant.

JP05-61482U describes a pump device in which a flow control valve is provided at an intermediate position in a drain passage that is connected between a suction passage and a discharge passage of a vane pump. With the pump device described in JP05-61482U, working oil discharged from pump chambers to the discharge passage in a manner proportional to the rotation speed of the pump is supplied to a hydraulic driving device through an orifice. In addition, with the pump device described in JP05-61482U, the flow control valve is controlled so as to be opened/closed such that the amount of the working oil supplied from the vane pump to the hydraulic driving device is controlled so as to be substantially constant.

SUMMARY OF INVENTION

However, with the pump device in JP05-61482U, a restrictor is provided in the discharge passage of the pump. Therefore, a pressure loss is caused at the restrictor, and torque required for driving the pump becomes correspondingly greater.

The present invention has been conceived in light of the problems mentioned above, and an object thereof is to provide a pump device capable of controlling a flow amount while reducing a driving torque for a pump.

According to one aspect of the present invention, a pump device that is configured to supply working fluid to a fluid pressure apparatus includes: a pump that is configured to discharge the working fluid into a discharge channel by sucking and pressurizing the working fluid; and a flow control valve that is configured to return a part of the working fluid discharged from the pump to a suction side; wherein the flow control valve comprises: a valve body; a first fluid pressure chamber that is provided so as to face against a first-side end surface of the valve body and that is communicated with the discharge channel; a second fluid pressure chamber that is provided so as to face against a second-side end surface of the valve body and that is communicated with the discharge channel; a biasing member that is accommodated in the second fluid pressure chamber in a compressed state for biasing the valve body in a valve-closing direction; and a pressure regulator that is provided in a communicating passage through which the discharge channel is communicated with the second fluid pressure chamber and that adjusts pressure in the second fluid pressure chamber.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a hydraulic circuit diagram of a pump device according to an embodiment of the present invention.

FIG. 2 is a map showing the relationship between the pump rotation speed and the pressure in a second fluid pressure chamber for the pump device at a certain target flow amount.

FIG. 3 is a map showing the relationship between the pressure in the second fluid pressure chamber and the applied current for a proportional solenoid.

FIG. 4 is a map showing the relationship between the required pressure for the pump device and the pressure in the second fluid pressure chamber.

DESCRIPTION OF EMBODIMENT

A pump device 100 according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a hydraulic circuit diagram of a pump device 100.

The pump device 100 includes a pump 1, in which working oil serving as working fluid is sucked from a suction channel 81 connected to a tank 4 and in which the working oil is pressurized and discharged to a discharge channel 82, and a flow control valve 2 that returns a part of the working oil discharged from the pump 1 to the suction channel 81 on the suction side and controls the flow amount of the working oil supplied to a fluid pressure apparatus 50 from the pump 1.

The pump 1 is a fixed displacement vane pump. The pump 1 includes a rotor 11 that is rotationally driven by a driving device, such as an engine (not shown), a plurality of vanes 12 that are provided so as to be movable in a reciprocating manner in the radial direction with respect to the rotor 11, and a cam ring 13 in which the rotor 11 is accommodated and tip ends of the vanes 12 are brought into sliding contact with a cam face 13 a on the inner circumference of the cam ring 13 by rotation of the rotor 11.

In the rotor 11, slits 14 having openings in an outer circumferential surface are formed in a radiating pattern with predetermined gaps. The vanes 12 are respectively inserted into the slits 14 in a freely slidable manner.

At the base-end sides of the slits 14, back pressure chambers 15 into which the discharge pressure of the pump 1 is guided are defined. The adjacent back pressure chambers 15 communicate with each other through an arc-shaped groove 16 formed in the rotor 11. The pump discharge pressure is constantly guided to the groove 16. The vanes 12 are pushed into the directions in which the vanes 12 project out from the slits 14 by the pressure in the back pressure chambers 15 and the centrifugal force caused by the rotation of the rotor 11, and thereby, the tip ends of the vanes 12 are brought into contact with the cam face 13 a on the inner circumference of the cam ring 13. With such a configuration, a plurality of pump chambers 17 are defined within the cam ring 13 by the outer circumferential surface of the rotor 11, the cam face 13 a of the cam ring 13, and pairs of adjacent vanes 12.

The cam ring 13 is an annular member whose cam face 13 a on the inner circumference has a substantially oval shape, and the cam ring 13 has suction regions 13 b and 13 d in which the volumes of the pump chambers 17 are expanded as the rotor 11 is rotated and discharge regions 13 c and 13 e in which the volumes of the pump chambers 17 are contracted as the rotor 11 is rotated.

While the rotor 11 is fully rotated, the respective pump chambers 17 suck the working oil from the suction channel 81 through a suction port (not shown) in the suction region 13 b of the cam ring 13, and discharge the sucked working oil to the discharge channel 82 through a discharge port 18 in the discharge region 13 c of the cam ring 13. Subsequently, the respective pump chambers 17 suck the working oil from the suction channel 81 through the suction port (not shown) in the suction region 13 d of the cam ring 13, and discharge the sucked working oil to the discharge channel 82 through the discharge port 18 in the discharge region 13 e of the cam ring 13. As described above, the respective pump chambers 17 are expanded/contracted by the rotation of the rotor 11, and the working oil is sucked/discharged twice while the rotor 11 is fully rotated. The pump rotation speed N of the pump 1 changes in accordance with the rotation speed of the driving device. As the pump rotation speed N is increased, the discharge flow amount of the pump 1 is increased in a manner proportional to the rotation speed.

As long as the pump 1 is of a rotationally-operated fixed displacement type, the pump 1 may be of any type, such as a gear pump.

The flow control valve 2 includes a spool 21 serving as a valve body inserted into a valve accommodating bore 25 in a freely slidable manner, a first fluid pressure chamber 23 that is provided so as to face against a first-side end surface of the spool 21, a second fluid pressure chamber 24 that is provided so as to face against a second-side end surface of the spool 21, and a return spring 22 serving as a biasing member accommodated in the second fluid pressure chamber 24 in a compressed state for biasing the spool 21 in the valve-closing direction.

The spool 21 includes a first land part 21 a and a second land part 21 b that slide along the inner circumferential surface of the valve accommodating bore 25.

In the first fluid pressure chamber 23, a first stopper portion 21 c is arranged by being connected to the first land part 21 a so as to be brought into contact with a bottom portion of the valve accommodating bore 25 when the spool 21 is moved in the direction in which the volume of the first fluid pressure chamber 23 is contracted and so as to restrict the movement of the spool 21 exceeding a predetermined amount.

A first communicating passage 83, which is branched off from the discharge channel 82, is connected to the first fluid pressure chamber 23 and a second communicating passage 84, which is branched off from the discharge channel 82, is connected to the second fluid pressure chamber 24. In addition, a drain passage 85, which is communicated with or shut off from the first fluid pressure chamber 23 by the first land part 21 a, is connected to the flow control valve 2.

The spool 21 is stopped at a position where the load exerted by the pressure of the working oil guided to the first fluid pressure chamber 23 and the second fluid pressure chamber 24, which are defined at both ends thereof, is balanced with the biasing force exerted by the return spring 22.

When the total load of the load exerted by the pressure in the second fluid pressure chamber 24 and the biasing force exerted by the return spring 22 is greater than the load exerted by the pressure in the first fluid pressure chamber 23, the return spring 22 is extended and the spool 21 is in a state in which the first stopper portion 21 c is in contact with the bottom portion of the valve accommodating bore 25.

In this state, the first land part 21 a of the spool 21 shuts off the communication between the first fluid pressure chamber 23 and the drain passage 85. Thus, all of the working oil discharged from the pump 1 is supplied to a the fluid pressure apparatus 50.

In contrast, when the load exerted by the pressure in the first fluid pressure chamber 23 is greater than the total load of the load exerted by the pressure in the second fluid pressure chamber 24 and the biasing force exerted by the return spring 22, the spool 21 is moved against the biasing force exerted by the return spring 22.

In this state, the first land part 21 a of the spool 21 allows communication between the first fluid pressure chamber 23 and the drain passage 85. Thus, a part of the working oil discharged from the pump 1 is returned to the suction channel 81 through the first fluid pressure chamber 23 and the drain passage 85.

The flow control valve 2 further includes a pressure regulator 3 that is provided in the second communicating passage 84 through which the discharge channel 82 is communicated with the second fluid pressure chamber 24 and that adjusts the pressure in the second fluid pressure chamber 24. The pressure regulator 3 includes an orifice 40 provided in the second communicating passage 84, a relief passage 86 that is branched off from the second communicating passage 84 at the downstream side of the orifice 40 and that communicates with the tank 4, and a relief valve 30 provided in the relief passage 86.

The relief valve 30 includes a spring 31 that exerts the biasing force in the valve-closing direction, a proportional solenoid 32 that exerts the biasing force in the valve-closing direction so as to be capable of changing the relief pressure Pr, and a pilot passage 33 through which the pressure in the relief passage 86 acts in the valve-opening direction.

The pressure P2 in the second fluid pressure chamber 24, which is pressure at the downstream side of the orifice 40, acts on the relief valve 30 through the relief passage 86 and the pilot passage 33 so as to exert the biasing force in the valve-opening direction.

When the pressure P2 in the second fluid pressure chamber 24 is greater than the relief pressure Pr that is determined by the total of the biasing force exerted by the spring 31 and the biasing force exerted by the proportional solenoid 32, the relief valve 30 is opened and the working oil in the second fluid pressure chamber 24 is discharged through the second communicating passage 84 to the tank 4. When the pressure P2 in the second fluid pressure chamber 24 is equal to the relief pressure Pr, the relief valve 30 is closed. In this way, the pressure P2 in the second fluid pressure chamber 24 is adjusted by the relief valve 30 so as to be equalized to the relief pressure Pr. It suffices that the total biasing force exerted by the proportional solenoid 32 and the spring 31 be in the valve-closing direction, and either the proportional solenoid 32 or the spring 31 may exert the biasing force in the valve-opening direction.

A controller 60 controls the applied current I applied to the proportional solenoid 32. In addition, the pump rotation speed N of the pump 1 detected by a pump-rotation-speed detector 70 and the signal for the pressure required by the fluid pressure apparatus 50 are input to the controller 60. The signal for the pressure required by the fluid pressure apparatus 50 will be described later.

A map (see FIG. 2) showing the relationship between the pump rotation speed N and the pressure P2 in the second fluid pressure chamber 24 of the pump device 100 at a certain target flow amount and a map (see FIG. 3) showing the relationship between the pressure P2 in the second fluid pressure chamber 24 and the applied current I for the proportional solenoid 32 are stored in advance in the controller 60. Here, the target flow amount is a predetermined value of the flow amount required by the fluid pressure apparatus 50, and in FIG. 2, the target flow amount corresponds to the flow amount discharged from the pump 1 at the pump rotation speed Nm.

In the pump device 100, the flow amount returning from the discharge channel 82 to the suction channel 81 is controlled by the flow control valve 2, and thereby, control is performed such that the flow amount of the working oil supplied to the fluid pressure apparatus 50 from the pump 1 through the discharge channel 82 becomes the target flow amount. Specifically, the controller 60 refers to the maps shown in FIGS. 2 and 3 and adjusts the pressure P2 in the second fluid pressure chamber 24 of the flow control valve 2 by controlling the relief valve 30, thereby controlling the flow amount returning from the discharge channel 82 to the suction channel 81.

The map shown in FIG. 2 will be described. In the pump 1, as the pump rotation speed N increases, the discharge flow amount also increases in a manner proportional to the rotation speed. Therefore, the controller 60 refers to the map shown in FIG. 2, and when the pump rotation speed N is greater than the rotation speed Nm that corresponds to the target flow amount, in order to increase the returning flow amount from the discharge channel 82 in accordance with the increase in the pump rotation speed N, the controller 60 performs control such that the set pressure for the pressure P2 in the second fluid pressure chamber 24 is decreased. In addition, when the pump rotation speed N is less than or equal to the rotation speed Nm, in order not to allow return of the working oil that has been discharged from the pump 1 to the discharge channel 82, the pressure P2 in the second fluid pressure chamber 24 is controlled so as to be constant.

Next, the map shown in FIG. 3 will be described. As shown in FIG. 3, the pressure P2 in the second fluid pressure chamber 24 and the applied current I for the proportional solenoid 32 of the relief valve 30 are in the proportional relationship. Specifically, in order to increase the pressure P2 in the second fluid pressure chamber 24, the applied current I for the proportional solenoid 32 is increased. By doing so, the relief pressure Pr of the relief valve 30 is increased, and in turn, the pressure P2 in the second fluid pressure chamber 24 is increased. In contrast, in order to reduce the pressure P2 in the second fluid pressure chamber 24, the applied current I for the proportional solenoid 32 is lowered. By doing so, the relief pressure Pr of the relief valve 30 is decreased, and in turn, the pressure P2 in the second fluid pressure chamber 24 is decreased.

Next, operation of the pump device 100 will be described.

The pump 1 is rotationally driven by a motive force from a driving device, such as an engine (not shown), and thereby, the working oil is sucked from the tank 4 through the suction channel 81 and the working oil is pressurized and discharged to the discharge channel 82. The working oil discharged into the discharge channel 82 is supplied to the fluid pressure apparatus 50.

The pump rotation speed N of the pump 1 is changed in accordance with the rotation speed of the driving device. As the pump rotation speed N is increased, the discharge flow amount of the pump 1 is also increased in a manner proportional to the rotation speed.

When the pump 1 is driven, the working oil is supplied to the first fluid pressure chamber 23 from the discharge channel 82 through the first communicating passage 83. With such a configuration, the equal amount of pressure acts on the first fluid pressure chamber 23 and the discharge channel 82. In addition, the working oil is supplied to the second fluid pressure chamber 24 from the discharge channel 82 through the second communicating passage 84. As for the pressure in the second fluid pressure chamber 24, when the pump rotation speed N is less than the rotation speed Nm, because the discharge flow amount of the pump 1 does not reach the target flow amount, the pressure in the second fluid pressure chamber 24 is not increased to the relief pressure Pr of the relief valve 30. Thus, because the working oil is not relieved from the relief valve 30, the pressure P2 in the second fluid pressure chamber 24 becomes equal to the pressure in the first fluid pressure chamber 23. In contrast, when the pump rotation speed N is greater than or equal to the rotation speed Nm, because the discharge flow amount of the pump 1 becomes greater than or equal to the target flow amount, in order to return a part of the discharge flow amount of the pump 1, the pressure P2 in the second fluid pressure chamber 24 is controlled by the relief valve 30. Therefore, the pressure P2 in the second fluid pressure chamber 24 becomes equal to the relief pressure Pr of the relief valve 30.

In addition, when the pump 1 is driven, the pump rotation speed N is input to the controller 60 from the pump-rotation-speed detector 70. The controller 60 refers to the map shown in FIG. 2 and selects the pressure P2 in the second fluid pressure chamber 24 corresponding to the input pump rotation speed N.

In the following, a case in which the pump device 100 is controlled with a medium-pressure characteristic B shown in FIG. 2 will be described. The medium-pressure characteristic B will be described later.

When the pump rotation speed N is the rotation speed Na that is less than or equal to the rotation speed Nm, the discharge flow amount of the pump 1 does not reach the target flow amount required by the fluid pressure apparatus 50. Therefore, as shown in the map in FIG. 2, in order not to return the flow amount discharged by the pump 1, the controller 60 selects the pressure Pd as the pressure P2 in the second fluid pressure chamber 24. Next, the controller 60 refers to the map shown in FIG. 3 and selects the applied current Id for the proportional solenoid 32 of the relief valve 30 corresponding to the pressure Pd. As described above, the controller 60 sets the relief pressure Pr of the relief valve 30 to the pressure Pd by applying the applied current Id to the proportional solenoid 32 of the relief valve 30. When the relief pressure Pr of the relief valve 30 is set to the pressure Pd, because the relief valve 30 will not be released until the pressure P2 in the second fluid pressure chamber 24 becomes the pressure Pd, the pressure in the first fluid pressure chamber 23 becomes equal to the pressure in the second fluid pressure chamber 24. Thus, although the biasing force in the valve-opening direction by the pressure in the first fluid pressure chamber 23 and the biasing force in the valve-closing direction by the pressure in the second fluid pressure chamber 24 are cancelled out, because the spool 21 is biased in the valve-closing direction by the biasing force exerted by the return spring 22, the spool 21 of the flow control valve 2 is not opened. Therefore, the working oil discharged by the pump 1 will not be returned.

When the pump rotation speed N is increased and becomes the rotation speed Nb that is greater than the rotation speed Nm, because the discharge flow amount of the pump 1 is greater than the flow amount required by the fluid pressure apparatus 50, the excessive flow amount is caused.

At this time, the controller 60 refers to the map shown in FIG. 2 and selects the pressure Pb as the pressure P2 in the second fluid pressure chamber 24 corresponding to the rotation speed Nb. In order to reduce the pressure P2 in the second fluid pressure chamber 24 from the pressure Pd to the pressure Pb, the controller 60 refers to the map shown in FIG. 3 and lowers the applied current I from the applied current Id for the proportional solenoid 32 of the relief valve 30 corresponding to the pressure Pd to the applied current Ib for the proportional solenoid 32 of the relief valve 30 corresponding to the pressure Pb. By doing so, the biasing force exerted by the proportional solenoid 32 is decreased and the relief pressure Pr is decreased. When the relief pressure Pr is decreased, the working oil is discharged from the second fluid pressure chamber 24 such that the pressure P2 in the second fluid pressure chamber 24 becomes the relief pressure Pr, and thereby, the pressure P2 in the second fluid pressure chamber 24 is decreased to the pressure Pb. As described above, the biasing force biasing the spool 21 of the flow control valve 2 in the valve-closing direction is decreased by an amount corresponding to the reduction of the pressure P2 in the second fluid pressure chamber 24 from the pressure Pd to the pressure Pb.

By doing so, although the discharge flow amount is increased due to the increase in the rotation speed of the pump 1 to the rotation speed Nb, because the spool 21 of the flow control valve 2 is opened and the working oil in the discharge channel 82 (the excessive flow amount) is returned to the suction channel 81 through the first fluid pressure chamber 23 and the drain passage 85, the flow amount of the working oil supplied to the fluid pressure apparatus 50 from the pump 1 is kept constant (at the target flow amount).

When the pump rotation speed N is further increased to the rotation speed Nc, the flow amount discharged from the pump 1 to the discharge channel 82 is increased even further. At this time, as shown in FIGS. 2 and 3, in order to reduce the pressure P2 in a second fluid pressure chamber 24 from the pressure Pb to the pressure Pe corresponding to the rotation speed Nc, the controller 60 lowers the applied current I from the applied current Ib to the applied current Ie. By doing so, the biasing force in the flow control valve 2 in the valve-closing direction is further decreased. Therefore, although the discharge flow amount is increased due to the increase in the rotation speed of the pump 1 to the rotation speed Nc, because the amount of the working oil returning from the discharge channel 82 to the suction channel 81 is also increased, the flow amount of the working oil supplied to the fluid pressure apparatus 50 from the pump 1 is kept constant (at the target flow amount).

In contrast, when, for example, the pump rotation speed N is decreased from the rotation speed Nc to the rotation speed Nb within a range in which the pump rotation speed is greater than the predetermined rotation speed Nm, the flow amount discharged from the pump 1 to the discharge channel 82 is decreased, and the excessive flow amount is also decreased. At this time, in order to increase the pressure P2 in the second fluid pressure chamber 24 from the pressure Pe corresponding to the rotation speed Nc to the pressure Pb corresponding to the rotation speed Nb, the controller 60 refers to the maps shown in FIGS. 2 and 3 and increases the applied current I for the proportional solenoid 32 of the relief valve 30 from the applied current Ie to the applied current Ib, thereby increasing the relief pressure Pr. As the relief pressure Pr is increased, the pressure P2 in the second fluid pressure chamber 24 is also increased accordingly. Therefore, the biasing force biasing the spool 21 of the flow control valve 2 in the valve-closing direction is increased in accordance with the amount of increase in the pressure P2 in the second fluid pressure chamber 24.

Thus, although the discharge flow amount is decreased due to the decrease in the rotation speed of the pump 1 to the rotation speed Nb, because the amount of the working oil returning to the suction channel 81 through the first fluid pressure chamber 23 is also decreased, the flow amount of the working oil supplied to the fluid pressure apparatus 50 from the pump 1 is kept constant (at the target flow amount).

As described above, even when the discharge flow amount of the pump 1 is changed due to the change in the pump rotation speed N of the pump 1, the pump device 100 can keep the flow amount supplied to the fluid pressure apparatus 50 constant. In addition, by using the relief valve 30, it is possible to adjust the pressure with a simple configuration.

When, for example, the pressure required by the fluid pressure apparatus 50 is increased while the flow amount is controlled so as to be constant (at the target flow amount), the pressure in the discharge channel 82 is increased and the pressure in the first fluid pressure chamber 23 is also increased through the first communicating passage 83. Thus, the biasing force biasing the spool 21 of the flow control valve 2 in the valve-opening direction is increased and the spool 21 is moved in the valve-opening direction. As the degree of opening of the spool 21 is increased, the returning flow amount returning to the suction channel 81 through the first fluid pressure chamber 23 and the drain passage 85 is increased, causing the flow amount through the discharge channel 82 to be changed. Therefore, even when the pressure is changed, in order to keep the flow amount constant, the pump device 100 selects the characteristics of the relationship between the pump rotation speed N and the pressure P2 in the second fluid pressure chamber 24 in accordance with the pressure. The specific description thereof is given below.

A signal for the pressure required by the fluid pressure apparatus 50 is input to the controller 60.

As the signal for the pressure required by the fluid pressure apparatus 50 is input to the controller 60, the controller 60 selects, from the map shown in FIG. 2 stored in advance, the characteristics of the relationship between the pump rotation speed N and the pressure P2 in the second fluid pressure chamber 24 in accordance with the pressure required by the fluid pressure apparatus 50.

For example, while the control is performed at the pump rotation speed Nb with the medium-pressure characteristic B, when the pressure required by the fluid pressure apparatus 50 is increased, the controller 60 selects a high-pressure characteristic A shown in FIG. 2. In other words, the set pressure for the pressure P2 in the second fluid pressure chamber 24 is changed from the pressure Pb with the medium-pressure characteristic B to the pressure Pa with the high-pressure characteristic A. By doing so, the biasing force biasing the spool 21 of the flow control valve 2 in the valve-closing direction is increased. Although the pressure in the discharge channel 82 is increased when the pressure required by the fluid pressure apparatus 50 is increased and the biasing force biasing the spool 21 in the valve-opening direction is increased due to the increase in the pressure in the first fluid pressure chamber 23, the pressure P2 in the second fluid pressure chamber 24 is correspondingly increased and the biasing force biasing the spool 21 of the flow control valve 2 in the valve-closing direction is increased. As described above, the degree of opening of the spool 21 of the flow control valve 2 is adjusted such that the returning flow amount does not change. Thus, it is possible to keep the flow amount through the discharge channel 82 of the pump 1 constant (at the target flow amount).

In addition, while the control is performed at the pump rotation speed Nb with the medium-pressure characteristic B, when the pressure required by the fluid pressure apparatus 50 is decreased, the controller 60 selects a low-pressure characteristic C shown in FIG. 2. In other words, the set pressure for the pressure P2 in the second fluid pressure chamber 24 is changed from the pressure Pb with the medium-pressure characteristic B to the pressure Pc with the low-pressure characteristic C. By doing so, the biasing force biasing the spool 21 of the flow control valve 2 in the valve-closing direction is decreased. Although the pressure in the discharge channel 82 is decreased when the pressure required by the fluid pressure apparatus 50 is decreased and the biasing force biasing the spool 21 in the valve-opening direction is decreased due to the decrease in the pressure in the first fluid pressure chamber 23, the pressure P2 in the second fluid pressure chamber 24 is correspondingly decreased and the biasing force biasing the spool 21 in the valve-closing direction is decreased. As described above, the degree of opening of the spool 21 of the flow control valve 2 is adjusted such that the returning flow amount does not change. Thus, it is possible to keep the flow amount through the discharge channel 82 of the pump 1 constant (at the target flow amount).

As described above, even when the pressure required by the fluid pressure apparatus 50 is changed, the controller 60 selects the characteristics of the relationship between the pump rotation speed N and the pressure P2 in the second fluid pressure chamber 24 in accordance with the pressure and controls the pressure P2 in the second fluid pressure chamber 24 on the basis of the selected characteristic, and thereby, it is possible to keep the flow amount through the discharge channel 82 of the pump 1 constant (at the target flow amount).

Although FIG. 2 shows stepwise characteristics like the high-pressure characteristic A, the medium-pressure characteristic B, and the low-pressure characteristic C, in practice, the characteristics are changed continuously between the high-pressure characteristic A and the low-pressure characteristic C. Of course, the characteristics may be changed in a stepwise manner. The medium-pressure characteristic B shown in FIG. 2 is only a conceptual illustration of a characteristic between the high-pressure characteristic A and the low-pressure characteristic C.

The above-mentioned embodiment is configured such that the signal for the pressure required by the fluid pressure apparatus 50 is input to the controller 60. Instead of this configuration, a pressure detector may be provided in the discharge channel 82, and the signal from the pressure detector may be input to the controller 60. As the signal is input from the pressure detector, the controller 60 refers to the map shown in FIG. 2 and selects appropriate characteristics of the relationship between the pump rotation speed N and the pressure P2 in the second fluid pressure chamber 24 in accordance with the pressure in the discharge channel 82 detected by the pressure detector. By doing so, it is possible to control the pump device 100 as in the case in which the signal for the pressure required by the fluid pressure apparatus 50 is input to the controller 60.

In addition, the pump device 100 may be configured such that a plurality of maps of the target flow amount shown in FIG. 2 may be stored in the controller 60 for each of different target flow amounts, and the controller 60 may appropriately select a map corresponding to the target flow amount in accordance with an instruction from the fluid pressure apparatus 50. In order to create a map with a different target flow amount, the position of the rotation speed Nm forming a break point of a graph may only be shifted to the position of pump rotation speed corresponding to the target flow amount.

According to the embodiment mentioned above, the advantages described below are afforded.

While a restrictor is conventionally provided in a discharge channel connecting a pump and a fluid pressure apparatus and a flow control valve is controlled on the basis of the pressure difference between the upstream side and the downstream side thereof, in this embodiment, because the flow control valve 2 includes the pressure regulator 3 that is provided in the second communicating passage 84 through which the discharge channel 82 is communicated with the second fluid pressure chamber 24 and that adjusts the pressure in the second fluid pressure chamber 24, it is possible to control the flow amount of the working oil supplied to the fluid pressure apparatus 50 from the pump 1 so as to be constant without providing a restrictor in the discharge channel 82. Furthermore, because a restrictor is not provided in the discharge channel 82, no pressure loss is caused, and it is possible to reduce the torque for driving the pump 1. In addition, it is possible to keep the flow amount constant even when the pressure required by the fluid pressure apparatus 50 is changed.

Although the pump device 100 performs a flow amount control in accordance with the pressure required by the fluid pressure apparatus 50 such that the flow amount of the working oil supplied to the fluid pressure apparatus 50 from the pump 1 is kept constant, if the fluid pressure apparatus 50 requires a pressure control to keep the pressure constant, by storing a map shown in FIG. 4 in the controller 60 in advance, it is possible to perform the pressure control to keep the pressure constant without performing the flow amount control. The specific description thereof is given below.

FIG. 4 is a map showing the relationship between the required pressure Pp for the pump 1 and the pressure P2 in the second fluid pressure chamber 24.

A signal for the required pressure Pp required by the fluid pressure apparatus 50 is input to the controller 60 from the fluid pressure apparatus 50.

As the signal for the required pressure Pp required by the fluid pressure apparatus 50 is input to the controller 60, the controller 60 controls the flow control valve 2 such that the pressure of the working oil supplied to the fluid pressure apparatus 50 becomes the required pressure Pp. Specifically, the controller 60 refers to the maps shown in FIGS. 4 and 3 stored in advance and performs control such that the pressure of the working oil supplied to the fluid pressure apparatus 50 becomes the required pressure Pp required. The controller 60 performs this control by controlling the relief valve 30, thereby adjusting the pressure P2 in the second fluid pressure chamber 24 of the flow control valve 2, and by controlling the biasing force in the valve-closing direction in the flow control valve 2.

Next, the pressure control of the pump device 100 will be described in detail.

When the pump device 100 performs the pressure control, the flow control valve 2 functions as a pressure control valve.

When the pressure in the discharge channel 82 is increased and becomes greater than or equal to the required pressure Pp required by the fluid pressure apparatus 50, in order to also increase the pressure in the first fluid pressure chamber 23, the biasing force exerted in the valve-opening direction of the spool 21 is increased. Because the pressure P2 in the second fluid pressure chamber 24 is controlled by the relief valve 30, the spool 21 is moved against the load exerted by the pressure P2 in the second fluid pressure chamber 24 and the biasing force exerted by the return spring 22. As the spool 21 is moved, the first fluid pressure chamber 23 is communicated with the drain passage 85. Thus, the working oil in the discharge channel 82 is returned to the suction channel 81 through the first fluid pressure chamber 23 and the drain passage 85, and the pressure in the discharge channel 82 is decreased.

When the pressure in the discharge channel 82 is decreased to the required pressure Pp required by the fluid pressure apparatus 50, the load exerted by the pressure in the first fluid pressure chamber 23 is balanced with the total load of the load exerted by the pressure P2 in the second fluid pressure chamber 24 in the valve-closing direction of the spool 21 and the biasing force exerted by the return spring 22, and the spool 21 is stopped at the balanced position. Thus, the flow amount with which the discharge pressure becomes the required pressure Pp is supplied to the discharge channel 82. As described above, even when the pressure in the discharge channel 82 is changed, it is possible to supply the required pressure Pp required by the fluid pressure apparatus 50 by adjusting the pressure in the discharge channel 82 by the flow control valve 2.

In addition, there is a case in which the required pressure Pp required by the fluid pressure apparatus 50 is changed. For example, when the signal for increasing the required pressure Pp from the pressure PM to the pressure PH is input to the controller 60 from the fluid pressure apparatus 50, the controller 60 first refers to the map shown in FIG. 4 and selects the pressure Ph in the second fluid pressure chamber 24 corresponding to the pressure PH. Next, the controller 60 refers to the map shown in FIG. 3 and selects the applied current Ih for the proportional solenoid 32 such that the pressure P2 in the second fluid pressure chamber 24 becomes the pressure Ph. The relief pressure Pr is increased by applying thus selected applied current Ih to the proportional solenoid 32 of the relief valve 30.

In contrast, for example, when the signal for decreasing the required pressure Pp from the pressure PM to the pressure PL is input to the controller 60 from the fluid pressure apparatus 50, the controller 60 first refers to the map shown in FIG. 4 and selects the pressure P1 in the second fluid pressure chamber 24 corresponding to the pressure PL. Next, the controller 60 refers to the map shown in FIG. 3 and selects the applied current I1 for the proportional solenoid 32 such that the pressure P2 in the second fluid pressure chamber 24 becomes the pressure P1. The relief pressure Pr is decreased by applying thus selected applied current I1 to the proportional solenoid 32 of the relief valve 30.

As described above, even when the required pressure Pp required by the fluid pressure apparatus 50 is changed, it is possible to control the pressure in the discharge channel 82 to the required pressure Pp required by the fluid pressure apparatus 50 by controlling the applied current I for the proportional solenoid 32 of the relief valve 30 in accordance with the required pressure Pp to control the relief pressure Pr, thereby controlling the biasing force in the valve-closing direction of the flow control valve 2.

The configurations, operations, and effects of the embodiment according to the present invention will be collectively described below.

The pump device 100 includes the pump 1, in which the working oil is sucked and the working oil is pressurized and discharged to the discharge channel 82, and the flow control valve 2 that returns a part of the working oil discharged from the pump 1 to the suction side (the suction channel 81), wherein the flow control valve 2 includes the valve body (the spool 21), the first fluid pressure chamber 23 that is provided so as to face against the first-side end surface of the valve body (the spool 21) and that is communicated with the discharge channel 82, the second fluid pressure chamber 24 that is provided so as to face against the second-side end surface of the valve body (the spool 21) and that is communicated with the discharge channel 82, the biasing member (the return spring 22) that is accommodated in the second fluid pressure chamber 24 in a compressed state for biasing the valve body (the spool 21) in the valve-closing direction, and the pressure regulator 3 that is provided in the second communicating passage 84 through which the discharge channel 82 is communicated with the second fluid pressure chamber 24 and that adjusts the pressure P2 in the second fluid pressure chamber 24.

With this configuration, the pressure P2 in the second fluid pressure chamber 24 of the flow control valve 2 is adjusted by the pressure regulator 3. The flow control valve 2 is controlled so as to be opened/closed in accordance with the pressure difference between the first fluid pressure chamber 23 into which the pressure in the discharge channel 82 is guided and the second fluid pressure chamber 24 into which the pressure Pr that has been adjusted by the pressure regulator 3 is guided. Therefore, it is possible to control the flow amount through the discharge channel of the pump 1 so as to be constant without providing a restrictor in the discharge channel 82. In addition, because a restrictor is not provided in the discharge channel 82, it is possible to reduce the torque for driving the pump 1.

In addition, the pump device 100 is characterized in that the pressure regulator 3 includes the orifice 40 that is provided in the second communicating passage 84 and the relief valve 30 that is provided in the relief passage 86, which is branched off from the second communicating passage 84 at the downstream side of the orifice 40, and that is capable of changing the relief pressure Pr.

In addition, the pump device 100 is characterized in that the relief valve 30 includes the proportional solenoid 32 that is capable of changing the relief pressure Pr.

With such a configuration, the pressure P2 in the second fluid pressure chamber 24 is adjusted by the relief valve 30. Therefore, by using the relief valve 30, it is possible to adjust the pressure with a simple configuration.

In addition, the pump device 100 is characterized in that the relief pressure Pr is adjusted by the relief valve 30 in accordance with the pump rotation speed N of the pump 1.

With such a configuration, even when the pump rotation speed N of the pump 1 is changed, by adjusting the relief pressure Pr in accordance with the pump rotation speed N, it is possible to keep the flow amount through the discharge channel 82 constant.

In addition, the pump device 100 is characterized in that the relief valve 30 changes the relief pressure Pr in accordance with the pressure required by the fluid pressure apparatus 50.

With such a configuration, even when the pressure required by the fluid pressure apparatus 50 is changed, by controlling the relief pressure Pr in accordance with the pressure required by the fluid pressure apparatus 50, it is possible to keep the flow amount through the discharge channel 82 constant.

The pump device 100 includes the flow control valve 2 and the pressure regulator 3 that is provided in the second communicating passage 84 through which the discharge channel 82 is communicated with the second fluid pressure chamber 24 and that adjusts the pressure in the second fluid pressure chamber 24, and thereby, it is possible to keep the flow amount through the discharge channel constant even when the pressure required by the fluid pressure apparatus 50 is changed.

Embodiments of this invention were described above, but the above embodiments are merely examples of applications of this invention, and the technical scope of this invention is not limited to the specific constitutions of the above embodiments.

In the above-mentioned embodiment, the pressure P2 in the second fluid pressure chamber is changed in accordance with the pump rotation speed N of the pump 1. Instead of this configuration, a flow meter that detects the flow amount discharged by the pump 1 may be provided, and the pressure P2 in the second fluid pressure chamber may be changed in accordance with the detected flow amount.

In the above-mentioned embodiment, the pressure regulator 3 includes the relief valve 30 and the orifice 40. Instead of this configuration, a configuration in which a three-way type proportional solenoid control valve, which controls the communication between the discharge channel 82 and the second fluid pressure chamber 24 and controls the communication between the second fluid pressure chamber 24 and the tank 4, is provided in the second communicating passage 84 may be employed.

This application claims priority based on Japanese Patent Application No. 2014-175449 filed with the Japan Patent Office on Aug. 29, 2014, the entire contents of which are incorporated into this specification. 

1. A pump device for supplying working fluid to a fluid pressure apparatus comprising: a pump configured to discharge the working fluid into a discharge channel by sucking and pressurizing the working fluid; and a flow control valve configured to return a part of the working fluid discharged from the pump to a suction side; wherein the flow control valve comprises: a valve body; a first fluid pressure chamber provided so as to face against a first-side end surface of the valve body, the first fluid pressure chamber being communicated with the discharge channel; a second fluid pressure chamber provided so as to face against a second-side end surface of the valve body, the second fluid pressure chamber being communicated with the discharge channel; a biasing member accommodated in the second fluid pressure chamber in a compressed state for biasing the valve body in a valve-closing direction; and a pressure regulator provided in a communicating passage through which the discharge channel is communicated with the second fluid pressure chamber, the pressure regulator being configured to adjust pressure in the second fluid pressure chamber.
 2. The pump device according to claim 1, wherein the pressure regulator further comprises: an orifice provided in the communicating passage; and a relief valve provided in a relief passage branched off from the communicating passage at a downstream side of the orifice, the relief valve being capable of changing a relief pressure.
 3. The pump device according to claim 2, wherein the relief valve further comprises a proportional solenoid that is capable of changing the relief pressure.
 4. The pump device according to claim 2, wherein the relief valve is configured to change the relief pressure in accordance with a rotation speed of the pump.
 5. The pump device according to claim 2, wherein the relief valve is configured to change the relief pressure in accordance with a pressure required by the fluid pressure apparatus. 